I have my own hypothesis on what it is about sexfighting that is so erotic and enticing. The simple version is that it combines catfighting and lesbian sex. Every straight man’s two favorite things. Why we love those two things are separate discussions in of themselves. The more complicated version goes something like this.

Most of the really popular stories here are very long and often the fights themselves are several pages worth of writing and last for hours in fictional time. The idea that women are that dedicated to sex is enticing to us. A woman that loves sex as much, if not more than we do is one of our greatest fantasies.

The competitive aspect of sexfighting is also attractive given that a lot of men are attracted to dedicated, badass women that are willing to give it everything they’ve got. If they’re powerful and persistent enough to fuck each other into oblivion just to prove themselves superior to their rival, what does that say about what they’ll do to please their men? It appeals to our basic animal instincts of finding a strong, capable mate.

That’s my best guess.